Steam-boiler stay bolt



March 1930- A. F. PJTKIN 1,750,687

STEAM BOILER STAY BOLT Fild Oct. 29, 1927 2 Sheets-Sheet 1 WITNESSES v(9r .1 M46 4 41/ March 18, 1930.

A. F. PITKIN 1,750,687

STEAM BOILER STAY BOLT Fi led Oct. 29, 1927 2 Sheets-Sheet 2 FIG. s.\

Patented Mar. 18, 1930 UNITED STATES ARTHUR F. PITKIN, OF SCHENECTADY,NEW YORK STEAM-BOILER STAY BOLT Application filed October 29, 1927.Serial No. 229,612.

This invention relates to steam boiler staybolts, of the articulated, orso-called flexible type, and its object is to provide a staybolt of suchtype, in the operation of which, binding or cramping between it and acoordinated member or members of a stay bolt structure, due to theaction of friction in operation, will be effectually prevented.

The improvement claimed is hereinafter fully set forth.

In the accompanying drawings: Figure 1 is a longitudinal centralsection, through a staybolt structure, illustrating an embodiment of theinvention; Fig. 2, a similar section, showing the members of thestructure, in their condition when preliminarily assembled; Fig. 3, atransverse section through the intermediate member, on the line IIIIIIof Fig. 1, the adjoining end member not being shown; Fig. 4, a similarsection, through the end member, 1, on the line IVIV of Fig. 1; Fig. 5,a section, taken similarly to Fig. 1, illustrating a modification ofdetail; and, Fig. 6, a similar section, showing the members of thestructure of Fig. 5 in their condition when preliminarily assembled.

In the operation of staybolt structures, of the general class or type towhich the present invention relates, objectionable results have beenexperienced, resulting from the action of friction between theordinarily applied ball shaped heads of the'bolt members, and theirsocket shaped seats. When the bolt is new, only a line contact isprovided between the surfaces of the bolt head and of the socket, but aswear in service occurs, the contacting surfaces become enlarged, and thefriction between them, under load, causes them to bind, and prevents thedesired and intended articulated action. This objection is overcome bythe present invention.

In the practice of the invention, referring descriptively to thespecific embodiment thereof which is herein exemplified, the stayboltstructure comprises the following three essential members or elements: afixed end member, 1, adapted to be secured to an inner boiler sheet, a;an intermediate member, 2, one end of which is articulated to themember, 1; and a fixed end member, 3, adapted to be secured in an outerboiler sheet, I), and articulated to the other end of the intermediatemember, 2. This broadly stated coordination of members was known in theart prior to the present invention, and the novelty thereof consists inthe structural features of articulation of the members, which will nowbe described.

The fixed member, 1, is in the form of a bolt, having an externalthread, 1 out upon it, at and adjoining one of its ends, which thread isscrewed into an inner sheet, a, of the boiler in which the structure isinstalled,

the threaded portion being made of sufficient length to extend, throughthe sheet, for a proper distance to enable a head, 1 to be formed on themember, by riveting it over, on the inner side of the sheet. A roundinghead, 1, is formed on the other end of the member, 1, said head being ofsufliciently greater diameter than the body of the member, to provide anannular bearing face, 1, which extends around the bottom of the head.The bearing face is substantially flat, that is to say, at a right angleto the axial line of the member, or, equivalently, curved, on acomparatively long radius, struck from said axial line. A tell-talehole, 1 is drilled, axially, in the member, 1, extending from its endfurther from the head, nearly to, or slightly into, the head.

The intermediate member, 2, of the staybolt structure is a bolt, havinga solid cylindrical body, and a head, 2, formed on each V of its ends,each of the heads being recessed to provide a socket, 2 for thereception of the head of an end member. Inwardly ex tending projectionsor flanges, 2, are formed on the ends of the sockets, the inner faces 9of said project-ions providing annular bearing faces, 2, on which thebearing faces of the end members abut, when assembled for operation.

The fixed end member, 3, comprises a tapered plug, 8, a short body orneck, 3 and a rounding head, 3, similar to the head, 1, of the endmember, 1, and formed with a similar annular bearing face, 3 The plugportion of the member is of tubular section, its shell being made onlysufficiently thick to safely resist the strain to which it is exposed inservice, and a tell tale hole, 3, is drilled in the member, extendingto, or nearly to, the head. The plug is fitted in an opening ofcorresponding form, in an outer sheet, Z), of the boiler, and is securedtherein, in the ordinary manner.

In assembling the structure for operation, the heads 1 and 3 of the endmembers, 1 and 3, are inserted, respectively, in the sockets, 2 of theintermediate member, 2, as shown in Fig. 2, and the end projections, 2,thereof, are swaged over the heads, so as to present the annular bearingfaces, 2 for contacting with the corresponding bearing faces, 1 and 3,of the end members, suflicient clearance being left between the headsand the sockets to allow relative movement, as shown in Fig. 1. Theassembled structure is inserted and secured in position in the boilersheets, by passing it through the opening in the outer sheet, until thelower end of the member, 1, on which there is formed a squared wrenchfit, 1 projects through the opening in the inner boiler sheet. This endis then gripped with a wrench, applied from the inside of the firebox ofthe boiler, and the member, 1, is screwed into the inner boiler sheet,until the member, 3, is drawn into place in the outer sheet, in which itis secured by welding, or other known means. The member, 1, is thenfurther screwed into the sheet, until the structure is drawn to theproper tension, after which the wrench fit, 1 is cut off, and the end ofthe bolt riveted over, or expanded to make a tight joint with the sheet,in the ordinary manner.

Figs. 5 and 6 illustrate a modification of structural detail, in whichthe intermediate member, 2, is made as short as possible, by eliminatingthe body portion and locating the end sockets closely together. Theformation of the annular bearing faces, and the manner of assembling thestructure, are the same as in the instance hereinbefore described.

lVhile the bearing faces of the articulated members are herein shown asbeing fiat, it is to be understood that they would similarly operate ifcurved on a comparatively long radius, and would constitute themechanical equivalent of fiat bearing surfaces. The application ofcurved bearing surfaces can be made without departure from the spiritand operative principle of the invention, and is, therefore, within thecontemplation thereof, the essential resultant in either instance being,that the coacting faces provide a rocking relative movement between thesections upon which the faces are formed without creating injuriousrelative sliding movement therebetween.

lVhat is claimed as the invention and desired to be secured by LettersPatent is:

1. An articulated staybolt having opposed end portions adapted to besecured respectively in the inner and outer sheets of a steam boiler,and a tension resisting intermediate section having a substantially flatface at each end, said end portions being provided at one end thereofwith a substantially fiat face engaging a corresponding face of thetension resisting section when in the assembled position, said co-actingfaces providing a rocking relative movement between the end portions andthe tension resisting intermediate portion Without creating relativesliding movement.

2. An articulated staybolt having opposed end portions adapted to besecured respectively in the inner and outer sheets of a steam boiler,and a tension resisting intermediate section having end sockets providedwith substantially fiat faces, said end portions being provided at oneend thereof with a head of substantially semi-spherical out line, thebottom surface of said head being substantially flat adapting it toengage the substantially fiat surface of thesocket when in assembledposition, said co-acting faces providing a rocking relative movementbetween the end portions and the tension resisting intermediate portionwithout creating relative sliding movement.

3. An articulated sectional staybolt comprising a tension resistingintermediate section having a substantially flat face at an end thereof,an adjacent tension resisting section having a substantially flat faceengagin the face of the said intermediate section when in the assembledposition, said coacting faces providing a rocking relative movementbetween the sections without creating relative sliding movement, and atension resisting section adjacent and connected to the opposite end ofthe intermediate section to permit articulation therebetween, theopposed ends of the said adjacent sections being adapted to be rigidlysecured respectively to the inner and outer sheets of a steam boiler.

4. An articulated sectional staybolt comprising a tension resistingintermediate section, an adjacent tension resisting section facesproviding a rocking relative movement between the sections Withoutcreating relative sliding movement, and a tension resisting sectionadjacent and connected to the opposite end of the intermediate sectionto permit articulation therebetween, the 0pposed ends of the saidadjacent sections being adapted to be rigidly secured respectively tothe inner and outer sheets of a steam boiler.

ARTHUR F. PITKIN.

